gba.cpp, Ln 2645:

Quote: case 0xC6:
{
bool start= ((DM1CNT_H ^ value) & 0x8000) ? true : false;
value &= 0xF7E0;

DM1CNT_H = value;
UPDATE_REG(0xC6, DM1CNT_H);

if(start && (value & 0x8000)) {
dma1Source = DM1SAD_L | (DM1SAD_H << 16);
dma1Dest = DM1DAD_L | (DM1DAD_H << 16);
CPUCheckDMA(0, 2);
}
}
break;

My personal logic tells me that the bold part is unneeded.

The bold part is needed. It fails if DM1CNT_H or value is >= 0x8000.

Look at the beginning.
start is only true if bit 15 of value is set, so it does not make sense to seperately check for that again in the bold part.

(08-18-2009 10:13 AM)spacy51 Wrote:  Look at the beginning.
start is only true if bit 15 of value is set, so it does not make sense to seperately check for that again in the bold part.

It tests bit 15 of (DM1CNT_H ^ value) and not just bit 15 of value.